1. Field of the Disclosure
Embodiments disclosed herein relate generally to systems and processes for characterization of a wellbore. More particularly, embodiments disclosed herein measure properties of gases produced during drilling, in addition to other drilling measurements, to characterize a wellbore. Such characterizations may be performed in real-time, allowing for the optimization of drilling parameters and improvement in drilling performance and the resulting well stability.
2. Background Art
Wellbore drilling, which is used, for example, in petroleum exploration and production, includes rotating a drill bit while applying axial force to the drill bit. The rotation and the axial force are typically provided by equipment at the surface that includes a drilling “rig.” The rig includes various devices to lift, rotate, and control segments of drill pipe, which ultimately connect the drill bit to the equipment on the rig. The drill pipe provides a hydraulic passage through which drilling fluid is pumped. The drilling fluid discharges through selected-size orifices in the bit (“jets”) for the purposes of cooling the drill bit and lifting rock cuttings out of the wellbore as it is being drilled.
The speed and economy with which a wellbore is drilled, as well as the quality of the hole drilled, depend on a number of factors. These factors include, among others, the mechanical properties of the rocks which are drilled, the diameter and type of the drill bit used, the flow rate of the drilling fluid, and the rotary speed and axial force applied to the drill bit. It is generally the case that for any particular mechanical properties of rocks, a rate at which the drill bit penetrates the rock (“ROP”) corresponds to the amount of axial force on and the rotary speed of the drill bit. The rate at which the drill bit wears out is generally related to the ROP. Various methods have been developed to optimize various drilling parameters to achieve various desirable results.
Prior art methods for optimizing values for drilling parameters have focused on rock compressive strength. For example, U.S. Pat. No. 6,349,595, issued to Civolani, el al. (“the '595 patent”), discloses a method of selecting a drill bit design parameter based on the compressive strength of the formation. The compressive strength of the formation may be directly measured by an indentation test performed on drill cuttings in the drilling fluid returns. The method may also be applied to determine the likely optimum drilling parameters such as hydraulic requirements, gauge protection, weight on bit (“WOB”), and the bit rotation rate. The '595 patent is hereby incorporated by reference in its entirety.
U.S. Pat. No. 6,424,919, issued to Moran, et al. (“the '919 patent”), discloses a method of selecting a drill bit design parameter by inputting at least one property of a formation to be drilled into a trained Artificial Neural Network (“ANN”). The '919 patent also discloses that a trained ANN may be used to determine optimum drilling operating parameters for a selected drill bit design in a formation having particular properties. The ANN may be trained using data obtained from laboratory experimentation or from existing wells that have been drilled near the present well, such as an offset well. The '919 patent is hereby incorporated by reference in its entirety.
Several references disclose various methods for using ANNs to solve various drilling, production, and formation evaluation problems. These references include U.S. Pat. No. 6,044,325 issued to Chakravarthy, et al., U.S. Pat. No. 6,002,985 issued to Stephenson, et al., U.S. Pat. No. 6,021,377 issued to Dubinsky, et al., U.S. Pat. No. 5,730,234 issued to Putot, U.S. Pat. No. 6,012,015 issued to Tubel, and U.S. Pat. No. 5,812,068 issued to Wisler, et al.
The data collection and analyses used in the above-described methods for simulating or analytically determining characteristics of a wellbore, while useful analytical and learning tools, often fail to properly characterize a wellbore. What is needed, therefore, are methods and apparatus useful for a more complete and accurate characterization of a wellbore.